PORTLAND, Maine — On Sunday, the last day of operation after 69 years at DiPietro’s Italian Sandwiches, Michele Grondin unlocked the door at 9 a.m. to find a line of customers already waiting.

At 2 p.m., customers were still coming from as far away as Connecticut to enjoy a last “Italian,” or one of the many variations the shop served at 171 Cumberland Ave. for nearly seven decades.

“We’re feeling exhausted and a bit overwhelmed,” Grondin, 39, said as she paused briefly between customer orders. “But we’ll be going strong until 7 p.m., or until we run out of bread. I think we’ll run out of bread first.”

Grondin’s grandparents founded the shop in 1944, and her father, Joseph DiPietro, took it over in 1966. Now 39, she joined the family business when she was 12.

Grondin said the store has been sold so that her mother, Eleanor DiPietro, can take a well-deserved rest. The shop was open seven days a week, and Eleanor ran it, with help from her grandchildren and Grondin, since 2003, when Joseph DiPietro died.

On Sunday afternoon, Eleanor DiPietro was busy with final details of the store’s closing.

“This was a hard decision for all of us,” Grondin said. “Still, it was really time.”

Generations of customers became regulars at the store, including such famous ones as former Boston Red Sox pitcher Bob Stanley. Grondin said they returned because DiPietro’s always used the same fresh, high-quality ingredients as when it started in 1944.

“We’re still using the same type of olives, the same pickles, on our sandwiches,” she said Sunday. “My father used to say, ‘if it ain’t broke, don’t fix it’ … consistency has really been the key.”

Now that long tradition has ended and the three-story building is under contract to be sold. The undisclosed buyer plans to renovate it, but keep the first floor as a store, according to Grondin. Apartments occupy the upper floors.

It’s not clear if the new store will sell Italian sandwiches. Meanwhile, customers will have to adjust to life without the DiPietro’s specialty.

Ben and Angela Davis are Portland natives now living in South Portland who returned Sunday to order their final two sandwiches.

“It’s one of the best Italian sandwiches in town,” said Ben, who is 58 and said he had been coming to DiPietro’s since he was 4.

“I remember Joe [DiPietro]. He and his wife were incredible people,” he said. “I remember a little boy or a little girl would come in, basically in rags, and he would always come around the counter and give them a sandwich or something to eat.”

Angela also remembered visiting DiPietro’s frequently as a young child. Her grandfather, a Greek immigrant, ran a barber shop across the street, at what is now Bayside Variety.

“This is sad, because [DiPietro’s] has been part of our local community and our history,” she said. “So we had to come by today. It’s a special occasion.”

A passerby agreed. Bob Hnatko, who works as a guide on historic tours of Portland, said DiPietro’s was part of the “old-world charm of this town.”

“The store has been such a well-known establishment for a long time,” he said. “There’s history here.”

The closing of DiPietro’s comes as another decades-old fixture on Munjoy Hill also changes hands.